I'll give you my 2 cents worth.
True story:
My wife bought "Toy Story" (1 and 2 ), and about 6 months after she bought them, I was going to do a backup. Toy Story 1 backed up perfectly. When I went to backup Toy Story 2, the media had a defect, and I couldn't read it
This DVD had played previously, but not anymore. There are no scratches on the surface at all, but if you look at the data side viewing it from an angle, you can clearly see the smeared surface internally. We lost our money
So now, EVERY DVD we buy, I back it up.
How long will the medias last
Good question
If the DVD manufacturers are creating crappy materials, 10 years from now DVDs will be worthless due to humidity and/or other atmospheric conditions.
Which brings me to this, again as I have previously posted: I have VHS tapes dated 1980, and they still play
With a lot of dropouts and noise, etc. but they still play after 20+ years.
Will DVD still play 20 years from now
Probably not, as they will probably have mold on them, and you wont be able to see a thing.
Welcome to the digital world
Gives you something to think about, doesn't it
-kwag